Non-insulating type switching power supply device
a non-insulating type, power supply device technology, applied in the direction of electric variable regulation, process and machine control, instruments, etc., can solve the problems of delay generation, switching loss cannot be set to zero, switching loss and switching frequency means an average loss, etc., to suppress switching loss and electromagnetic noise.
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first embodiment
[0046]FIG. 1 is a block diagram illustrating a configuration of a switching power supply device 10 according to a first embodiment. The switching power supply device 10 is a non-insulating step-down switching power supply device to convert an input voltage Vin into an output voltage Vout with synchronous rectification method. In FIG. 1, the switching power supply device 10 includes a high-side switch SW1 and a low-side switch SW2 directly connected between a voltage source of the input voltage Vin and a ground terminal, an inductor L1 connected between an output terminal VOUT and a junction node LX between the switches SW1 and SW2, a capacitor C1, connected to the junction node LX, that constitutes a resonant circuit with the inductor L1, and a capacitor C2 that smoothes the output voltage Vout at the output terminal VOUT. The switches SW1 and SW2 are, for example, Metal-Oxide Semiconductor Field Effect Transistor (MOSFET).
[0047]In addition, the switches SW1 and SW2 have on-resistan...
second embodiment
[0081]FIG. 7 is a block diagram illustrating a configuration of a switching power supply device 10C according to a second embodiment. In the switching power supply device 10 according to the first embodiment, using PFM control, the switching frequency fluctuates. By contrast, in the switching power supply device 10C according to the second embodiment, in order to keep the switching frequency at a constant value, the length of ON-period of the switch SW1 is kept and is controlled so that the lower limit of the inductor current Ilx fluctuates. Under an ideal condition in which the on-resistances of the switches SW1 and SW2 are zero, when the input voltage Vin and the output voltage Vout are determined, the duty ratio is determined. Accordingly, if the ON-period of the switch SW1 is constant, an OFF-period of the switch SW1 is constant. That is, in the switching power supply device 10C according to the second embodiment, by setting the length of 1 cycle of the operation of the switchin...
third embodiment
[0103]FIG. 11 is a block diagram illustrating a configuration of a switching power supply device 10F according to a third embodiment. In the above-described first and second embodiments, the switching power supply devices 10(10A, 10B, 10C) are step-down switching power supply devices. The switching power supply device 10F shown in FIG. 11 is configured as a step-up switching power supply device, based on the switching power supply device 10C shown in FIG. 7.
[0104]In FIG. 11, the switching power supply device 10F includes the inductor L1 and a switch SW51 connected in series between the voltage source of the input voltage Vin and the ground terminal, a switch SW52 connected between the output terminal VOUT and the junction node LX between the inductor L1 and the switch SW51, a capacitor C1, connected to the junction node LX, that constitutes a resonant circuit with the inductor L1, and a capacitor C2 that smoothes the output voltage Vout at the output terminal VOUT. The switches SW51...
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